Levenshtein-distance: New exercise suggestion

[marcelritzschke]

No description provided.

[rpottsoh]

Just a quick glance, I see some minor formatting changes that would be good for the canonical data.

[rpottsoh]

It would be a nice if the opening comment to this PR gave some background information regarding this exercise.

Also, presently, adding new exercises is on hold in a general sense for the site. However, it doesn't mean that individual language tracks can't still add this exercise now if they so choose.

[marcelritzschke]

Thanks a lot for reviewing of my PR! I tried to follow your suggestions

[yawpitch]

We can't merge this until #1560 lifts, but it's a great idea for an exercise. My one thought, should it just be levenshtein rather than levenshtein-distance, along the same lines as hamming not being hamming-distance?

[marcelritzschke]

@yawpitch Renaming du just levenshtein is a good point, since I don't know anything else which is associated to Levenshtein. I will do the changes and we can wait for #1560

[petertseng]

As of f18d301, the cases in this file are correct, according to:

require 'json'
require_relative '../../verify'

# https://web.archive.org/web/20180612143641/https://bitbucket.org/clearer/iosifovich/
def lev_dist(shorter, longer)
  shorter, longer = [longer, shorter] if shorter.size > longer.size
  left = 0
  right = -1
  left += 1 while shorter[left] &.== longer[left]
  right -= 1 while left - right <= shorter.size && shorter[right] == longer[right]

  buf = Array.new(shorter.size + 2 - left + right, 0)
  #puts "compare #{left} to #{right}: #{shorter[left..right]} vs #{longer[left..right]} (#{buf.size})"

  (left..(longer.size + right)).each { |i|
    clong = longer[i]
    tmp = buf[0]
    buf[0] += 1

    (1...buf.size).each { |j|
      cshort = shorter[left + j - 1]
      r = buf[j]
      buf[j] = [
        r + 1,
        buf[j - 1] + 1,
        tmp + (clong == cshort ? 0 : 1),
      ].min
      tmp = r
    }
  }

  buf[-1]
end

json = JSON.parse(File.read(File.join(__dir__, 'canonical-data.json')))

verify(json['cases'], property: 'distance') { |i, _|
  lev_dist(i['from'], i['to'])
}

[SleeplessByte]

@n4bla #1560 has been resolved!

[SleeplessByte]

Closed and re-opened to make CI run.

[ErikSchierboom]

@marcelritzschke Are you still interested in working on this PR? If so, I've created a branch that adds four new commits that get your PR up-to-date with the latest specs: https://github.com/exercism/problem-specifications/commits/exercise-levenshtein-distance You chould cherry-pick those commits onto your branch to update your PR.

[IsaacG]

This appears abandoned. I'll close this out. If you still want to work on this, we can reopen.